Large wattage filament lamps use heavy filaments to produce large amounts of light. A large amount of heat is also produced, so it is necessary to enclose the filament in a large volume envelope. The filament is then mechanically supported, and electrically connected in the large volume by long metal rods. The heavy filament structure on the end of the long support rods produces a relatively large moment that can bend or twist the supports, or misalign the filament. This twisting and bending can also break down the seal structure of the lamp, where the metal rods, acting as electrical conduits pass through the envelope to the exterior. It is therefore common practice to include spring arms or similar braces that extend from the filament supports to the inside wall of the envelope. These braces limit the amount of sway the filament can go through, and therefore limit the amount of twisting or bending that can be applied to the seal structure. There is then a general need for an incandescent lamp with shock resisting supports.
High wattage studio lamps require substantial support of the filament throughout the lamp's life. Unlike stadium lights, or other large wattage fixed position lamps, studio lamps are treated roughly. They are frequently moved from one set to another, and similarly repositioned on a set. Unfortunately, the standard metal supports cannot maintain the needed support since in time the temperature eliminates the spring tension. The high operation temperature anneals the metal springs over their life, and they loose their ability to cushion the filament structure. This is particularly true of smaller, more highly tensed springs. Spring systems then tend to be effective only during the early life of the lamp. Large spring structures are additionally more costly due to the design and assembly complexity, and the larger material cost. The interaction between the metal supports and the envelope can also abrade the envelope, and making a possible failure point on the glass envelope. There is then a need for an improved support structure for studio lamps.
To extend the life of a filament lamp, or alternatively to increase its luminous output, halogens are commonly included in the envelope. The halogen chemical cycle is well known in lamp making. To not interfere with the halogen cycle, the braces and other support materials are therefore made of molybdenum or tungsten, both of with are expensive materials. As lamps get larger, the molybdenum or tungsten bracing structures become increasingly expensive. There is then a need for an incandescent lamp with shock resisting supports that do not interfere with the enclosed chemistry, and there is a need for such supports that use a minimal amount of expensive materials.
Examples of the prior art are shown in the following U.S. patents.
U.S. Pat. No. 3,543,962 issued to Carl L. Peterson on Dec. 1, 1970 for a High Wattage Quartz Halogen Lamp shows a studio lamp with the filament structure braced against envelope wall by the end arms of coiled springs.
U.S. Pat. 3,717,784 issued to W. G. Matheson on Feb. 20, 1973 for a Tungsten Halogen Lamp With Tungsten Mesh Deflector shows a studio lamp with glass legs sealed by molybdenum cups.
U.S. Pat. No. 4,023,060 issued to Bernard Pike on May 10, 1077 for a Ruggedized High Power Tungsten Halogen Lamp shows a studio lamp with glass legs sealed by molybdenum cups. The upper support rods ends are captured in cavities, and the side sections are braced against the glass envelope by spring arm ends.
U.S. Pat. No. 4,720,653 issued to Jeffrey P. Buschmann on Jan. 19, 1988 for an Electric Lamp Support Member Providing Both Compressive and Axial Support shows a studio lamp with glass legs sealed by molybdenum cups. The upper support rods ends are braced against the glass envelope by looping spring arms.
U.S. Pat. No. 4,758,760 issued to David A. Cox and Jeffrey P. Buschmann on Jul. 19, 1988 for a Convectively Cooled Ceramic Lamp Base shows a studio lamp with glass legs sealed by molybdenum cups. The upper rod ends are braced against the glass envelope by spring arms, and the glass legs are captured in a ceramic base.
U.S. Pat. No. 4,985,656 issued to Arnold Westlund Jr. and Jeffrey P. Buschmann on Jan. 15, 1991 for a Lamp with Re-Enforced Tubular Base Pins shows a studio lamp with glass legs sealed by molybdenum cups. The upper rod ends are braced against the glass envelope by spring arms, and the glass legs are captured in a ceramic base.